High temperatures, lower humidity and greater instability increase the potential for fires to grow, said Ed Delgado, the national predictive services meteorologist for the National Interagency Fire Center in Boise, Idaho.

"Our biggest concern right now is existing fires," he said. "We're not expecting lightning over the next few days, although that doesn't alleviate the potential for human-caused fires, especially as we get into camping and hunting seasons."

Seven homes were destroyed and hundreds of people were evacuated near Casper, Wyo., where a wildfire burned almost 24 square miles. In western Montana, fire crews were struggling to control a blaze that prompted an evacuation order for 400 houses west of Hamilton.

In eastern Washington, a grass and sagebrush fire that ballooned from 11,000 acres to more than 60,000 - or 95 square miles - before winds died down was blamed for destroying three homes near Grand Coulee, a fire official said.

As winds eased, crews were hopeful they could gain ground on dozens of fires sparked by weekend lightning storms. But more evacuation orders were issued Tuesday as a wildfire moved into the hills west of Wenatchee, a fruit capital on the banks of the Columbia River.

More than 150 homes were evacuated as the fire burned about 140 miles east of Seattle. About 160 firefighters gathered to help fight the blaze, which covered 1,000 acres.

Only a shed has been lost near Wenatchee, and no injuries were reported at what appeared to be the most threatening of numerous lightning-sparked wildfires in the state.

In Montana, Sawtooth Fire spokesman Gregg DeNitto with the U.S. Forest Service said there was no word on when residents there might be allowed to return. The fire exploded over the past two days from just over 1 square mile to more than 6, although no houses were reported lost.

DeNitto said most threatened houses were a half-mile to one mile from the fire's edge.

An estimated 1,000 people live within the evacuated area, although Ravalli County Commissioner Suzy Foss said not all of them left. Of those who fled, most were staying with friends, relatives or acquaintances, Foss said.

Only a couple of residents spent the night at a Red Cross shelter set up in Hamilton for evacuees, DeNitto said.

Firefighters got help from the weather in Wyoming, where cooler temperatures and calmer winds bought time to put more people and equipment into action around two large fires. As many as 750 homes were threatened by the large wildfire near Casper. Some 400 people were evacuated from 150 homes.

In central Oregon, smoke settled in the town of Sisters for about six hours Tuesday as crews battled a forest fire on about 4,300 acres southwest of town. Sisters has about 2,000 residents and is a center for tourists and outdoor recreation.

The Oregon Department of Environmental Quality said atmospheric conditions - a temperature inversion - could mean poor air quality in the mornings through Saturday.